


A King's Summons

by MeGaLoTrash



Category: Undertale (Video Game)
Genre: Ecto-Genitalia (Undertale), M/M, Masturbation, Mutual Pining, Rough Sex, Sensitive bones, Sexual Tension, Size Difference, Size Kink, Voyeurism
Language: English
Status: Completed
Published: 2018-06-03
Updated: 2018-06-03
Packaged: 2019-05-17 17:37:26
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,087
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14836157
Author URL: https://archiveofourown.org/users/MeGaLoTrash/pseuds/MeGaLoTrash
Summary: Gaster has been called upon to see the King, something that happens regularly and that he's grown quite fond of.But he knows a summons to Asgore's private chambers, at night, is something entirely different but not unexpected...A Kingdings fic for someone who wants to stay anonymous, thank you so much and hope you enjoy it!





	A King's Summons

Gaster’s footsteps echoed around a softly lit hall on the way that lead up to the throne room. During the day the hall was filled with the hustle and bustle of the royal court, something which Gaster avoided attending whenever he could, but in this late hour was completely vacant. The only sound the royal scientist had for company other than his footsteps was the pounding of his soul. It wasn’t his discomfort for court that had him rattled, but the reason why he was walking its halls at night. Gaster knew he shouldn’t have come; if he was spotted there was going to be all sorts of unpleasant repercussions, not to mention the risk he was taking considering his profession. 

But it wasn’t like he could ignore a direct summons from the King though. 

The King’s messenger had delivered the handwritten letter to Gaster’s lab less than an hour ago. The messenger didn’t wait for Gaster’s reply, which should have aroused his suspicions. However, he had brushed it off as the King had sent him confidential letters in the past. Gaster wasn’t exactly wrong; Asgore’s message was just confidential for different reasons than he had expected. With no way to ask the King to clarify what he meant by a ‘private meeting’ Gaster either had to come up with a way to excuse for his absence, or go Asgore find out himself. 

The problem with his first option was Gaster had no believable excuses to avoid going to the capital. He was currently waiting on results concerning some very delicate experiments. But they took time, and his team was already doing the monitoring for him. Gaster was so anxious about wanting his experiments to succeed. As a result, he had been going through a bout of debilitating insomnia. A change of pace and scenery would help with his issue. Gaster just wasn’t sure going to spend time with the King in the middle of the night was what he would call an ideal solution.

However, tonight was a long time coming. No matter how much Gaster tried to ignore the long-standing feelings he had for Asgore, the truth of the matter was he cared about the King more than was appropriate. He was used to dismissing all of his biological whims as trivial matters not worth his time. But That was becoming increasingly harder the more time he spent with the King, and worse, his attraction was rapidly developing on a physical level as well. Their spending vast amounts of time together had been necessary at first. Gaster was making some major improvements to the core that needed the King's approval so they met at least three times a week. Formal meetings turned into discussing business over tea in the king’s home, which turned into meeting up for no other reason than to spend time together. 

It wasn’t that Gaster minded at all; Asgore was excellent company and the time they spend together was incredibly soothing. He was used to being someone formidable, one who would tower over other monsters and unintentionally scare them with his intense passion for the betterment of monster kind. However, his relationship with Asgore had none of the restraints he ran into when interacting with anyone else. The King dwarfed him in both stature and status and yet he always managed to make Gaster feel important when they were together. For someone who was used to taking charge in everything he did, his time with Asgore was like indulging in the other side. Letting someone else take care of him. Gaster had even encouraged this behaviour, finding his soul skipping a beat whenever he had the King’s full attention. 

Gaster had originally thought of their interactions as harmless flirting, something to pass the time and ignite the senses. He stuck to those thoughts despite the lingering glances, the ‘accidental’ touches, and the tingling feeling he got when the king loomed over him. Gaster wasn’t sure exactly when he started to crave the King overpowering his smaller frame, but it had seeped into every aspect of his life. Even going to the Asgore’s home would be enough to set Gaster’s desire’s ablaze. A humble abode, but one that was built for a monster so much bigger than himself. He would get chills just sitting with Asgore in a chair where he was only just able to reach the floor.

But tonight Gaster was going somewhere different, somewhere that lacked the open door policy Asgore had for his main home. He was heading to the King’s private quarters. Gaster knew from their talks that the Asgore spent at least one night a week here to be able to unwind in the solitude. Which was another reason why he shouldn’t be going; this was a place where Asgore went to be away from his subjects. As far as Gaster knew no one else had joined the King in his private chambers for a long time. Anyone with half a brain would be able to figure out what an invitation like this meant. While Gaster’s soul was rejoicing in getting what he had been craving, his mind was very hesitant to follow through. Even if it was what they both obviously wanted. 

Gaster’s window to back out was closing just as fast as the ornate door was approaching. He hadn’t ever really taken more than a fleeting glance at the door before him in the past, but now he was studying all its ornate features in detail. His mouth felt dry when he noticed just how tall it was, easily two or three times his relatively large stature. Gaster knew he was stalling for extra time but he felt compelled to check the surrounding area for stray guards or lost courtiers before knocking. Finding the halls empty gave Gaster no further excuses, he raised a shaky hand to the door and knocked as loud as he dared. 

“Come in.”

The reply was instant, Gaster didn’t know why he expected anything different. Asgore had stated he was waiting for him in the letter, but no amount of analytical thinking was giving any sense of tone to the two words heard through a heavy door. If Gaster wanted to confirm why he was asked here tonight then he was going to have to cross the threshold. He let out a breath he didn’t know he’d been holding and pushed open the door to find a surprisingly cosy setting. There was no formality of the throne room, nor the neat and tidy setting of Asgore’s home. In its place were lavish cuts of cloth draped from the ceiling, cushions littering the floor and furniture, and a roaring fire as the centerpiece. 

Asgore was sat in the middle of the organised chaos with a welcoming smile on his face as he beckoned his companion closer. Gaster had to stop himself from doing a double take when he realised what the King was wearing. His usual heavy royal armour had been discarded and replaced with a casual robe of deep purple. One that Asgore had neglected to close all the way, leaving a slither of his bare chest exposed. Gaster could feel magic dancing across his bones in response to the irresistible sight in front of him, his soul quickening when he felt the stirring of something low in his pelvis. 

_Gods help him_.

“Can I make you a drink? some tea or water perhaps?” Asgore rose to his feet as he spoke, his demeanor dancing the line between inviting and intimidating the closer he got. “Or would you prefer something stronger?”

Gaster swallowed on dry air as the King got closer to him, his body refusing to do anything but shake with anticipation. He didn’t expect that seeing Asgore would completely overthrow his ability to function normally, but as the King drew closer he could feel himself shutting down. Instinct was drawing them close enough to touch, but Gaster was still startled when one of the King’s large hands reached towards him. Gaster held his breath when Asgore cupped his skull, a soft whine filling the space when the King started to rub his thumb across his cheekbone. He mortified when he realised the noise had come from _him._

“Your Majesty-” Gaster’s voice was unsteady, a contrast from his body’s willingness for whatever the King wanted to give him. But he had to be the voice of reason, even if every fiber of his being wanted this. There was too much at risk.“I-I’m not sure it would be proper if I st-stayed any longer.”

“That’s completely understandable Doctor, I wouldn’t want you to stay if you are uncomfortable” 

Asgore’s hot breath tickled Gaster’s bones as he stooped to look into his companion’s face, the soft smile and kind eyes demonstrating the truth in his words. But the heat wasn’t fading between them. No matter what Gaster tried to tell himself he just couldn’t pull away, and it was obvious the King felt the same. The hand that Asgore had on his cheek had trailed downwards until it was resting lightly on Gaster’s spine. The King’s grip wasn’t forceful but it was firm, the pressure just enough to leave Gaster wanting but not so hard that he couldn’t escape. But _gods_ did Gaster need the King to take charge and take what he wanted from him. 

“I want you to know that I didn’t ask you here tonight as your king, but as one monster reaching out to another for companionship.” Gaster watched as what looked far too much like a smirk play over his King’s features. “And more, if you want it.”

At this point there was no denying they were in a lover’s embrace. Gaster could feel parts of the King’s warm fur radiating heat into his cool bones, making another whine escape his open mouth. They had denied themselves for so long, they both wanted this, and Asgore had taken every precaution he could to keep tonight a private affair. Who was Gaster to deny them any longer on principle alone?

“I-I want this-” Gaster moved his trembling hands to where the King’s robe was parted to let his hands tangle in the plush fabric. “-So much.”

A genuine smile flickered onto Asgore’s face as he worked on closing the final gap between them.“Well, that’s good to hear.”

Asgore pressed his mouth against Gaster’s teeth in a bruising kiss second’s later. Gaster was lucky his kind had little need for respiratory functions when the King’s shuddering moan took his breath away. His mind might have been shutting down but his magic had already gone through the process of forming a tongue which Asgore gladly wrapped his own around. Just like the other contrasts in temperature they had, Asgore’s tongue was searingly hot against Gaster’s own. A flickering thought crossed his mind about not minding if the King’s magic leaving marks on him, but it was pushed out for the realisation that he was being picked up off his feet. 

Gaster whimpered into the kiss and let his legs wrap around Asgore’s sturdy frame. For someone who towered over most monsters, having someone pick him up like he was nothing but a rag doll was both disorientating and thrilling. This kind of treatment was exactly what Gaster had been craving. He could feel one of the King’s arms supporting him fully as the other worked its way underneath his sweater. Asgore’s touches were as desperate as Gaster felt, but there was still a tenderness to him. One that was making him tremble as the King brought them into the bedroom and laid him on the luxurious bed.

Asgore didn’t part their kiss right away but it became apparent that some separation was needed if they wanted to go further. Soon they were a panting mess of limbs and half pulled off clothing. Gaster wished he had dressed more appropriately for the occasion, but then changing clothing had been the furthest thing from his mind when he received the summons earlier. Asgore didn’t seem to mind though; he managed to pull Gaster’s sweater off without much issue, only starting to fumble when it came to removing the scientist’s pants. Asgore reluctantly pulled away so Gaster could finish the job, but not before lightly grinding his hips against the body underneath him. Gaster realised that the King’s size definitely extended to _every_ part of him. 

“You look amazing-” Asgore said with a voice laced with lust when Gaster finished stripping himself bare.“I am afraid I’m unfamiliar with your kind’s biology.” Gaster had managed to hold back from letting his magic fully settle on anything until now but Asgore was transfixed on where it was settling in his pelvis.“But you won’t be opposed to giving me a demonstration would you, Doctor?”

Asgore’s blatant flirting had Gaster’s skull flushing despite the situation they were in. In his fantasies the King was always passionate and intense, yet he hadn’t anticipated Asgore’s playful nature to crossover into the bedroom. But the king had given Gaster the upper hand by asking for his guidance, and he wasn’t one to pass up the opportunity to monopolise other’s attention. 

He just didn’t expect to get the opportunity to do so to try and entice his king. 

“It’s quite simple _your highness_ ” Gaster watched Asgore’s reactions carefully when he used the honorific, the subtle shudder he gave being a dead giveaway that he was aroused by it. “My kind has wells of magical reserves which make up our attacks and our bodies.” he trailed a hand down his spine, whimpering softly with his sensitive spots heightened by his audience. Gaster pause when he got to his pelvis, his magic settled into a tingling entrance that Gaster was eager to start stimulating. “This type of magic is usually invisible, but -ah- remarkably adaptable.”

Gaster’s skull was burning hot from spreading himself open for the King to see but Asgore was absolutely hypnotised by watching his fingers slipping inside the magical construct. If what Gaster had felt earlier really was the King’s cock, then he really needed to concentrate on stretching himself out adequately. But his attention kept wavering when all he wanted to do was to feel Asgore inside of him instead of his own hand. By the time Gaster had added a third finger he was begging the King with his eyes, silently asking for what he couldn’t quite bring himself to say. Asgore could only take a few more moments of watching him squirm before he snapped, pouncing on top of him with a hungry smirk on his face. 

“I see” Asgore was still playing their game while pulling apart his robe, pushing Gaster’s hand to the side to press his throbbing cock against the entrance in his pelvis. “I think some more practical learning is in order.” 

That was the only warning the King gave before Gaster felt an immense pressure in his lower half. There was a moment’s panic over whether Asgore was going to actually fit but then Gaster was clawing at the King’s back when his magic gave way.

“Sire!”

Asgore wasn’t even all the way in and Gaster was already seeing stars in his vision. He barely registered the King’s whispered apologies over the searing heat clouding his mind, him but he knew it was only a courtesy. Asgore must have been able to feel the way Gaster’s magic was clinging to his cock so tightly like it couldn’t bear to let him go. It was incredible, but the King was shaking from holding back on his behalf. Gaster needed to push aside any lingering hesitation to get what he truly wanted. 

“Please move,” Gaster arched his body against his king, keening embarrassingly when he felt Asgore’s cock push further inside him. “Oh gods A-Asgore! Please, More!”

The King’s restraint started to waver as he groaned deeply next to Gaster’s skull. Asgore moved back on his haunches, grabbed hold of Gaster’s hips, and started to impale him on his cock. Gaster arched into his King, moaning loudly when he glanced down to see Asgore’s cock moving in his translucent magic. The King was just as big and he felt, and Gaster knew he was never going to be able to have a purely professional relationship after feeling the King inside him fully. Considering they had both lived in celibacy for years up until now it wasn’t surprising that they were both falling apart so soon, but that logic didn’t make it any less intense. 

As they both neared the edge Asgore was all but picking Gaster off the bed fully, taking his pleasure from his smaller form just like Gaster wanted. The King’s cock had been steadily driving Gaster towards delirium but a slight change of angle was all it took for him to cum hard. Gaster was surprised his bones all stayed in place with the intensity of his climax, only to have it extended when he felt Asgore’s hot cum filling him up to the brim. The King collapsed forward when he was done, his beard tickling Gaster’s over-sensitive skull as he whispered sweet nothings to the still shaking scientist.

Gaster felt an odd sense of emptiness when the King pulled out of him even while his magic started to dissipate, like he didn’t want to deal with the reality of tonight being over. A sorrow washed over him when he watched the King fasten his robes again and move to stand. Gaster couldn’t help feeling like he might be overstaying his welcome, that he needed to leave even though his soul was crying out at the thought of separation. 

“Sir- Asgore-” Gaster started sheepishly, not wanting to hear the answer he expected when he saw the King facing away from him. “Would you like me to leave?”

“Oh goodness no!”Asgore turned back to him with a worried look on his face, as if he was startled that Gaster would think that way. “I’m afraid I have terrible insomnia since-” 

Asgore trailed off as he tried to explain but Gaster knew just what he meant. The pain of losing those you loved was something they shared. Gaster moved forward and slipped his hands into the King’s as an offer of reassurance, stuttering himself when Asgore brought them to his face to place soft kisses on his bones. 

“I do have a special brew of tea that helps though. Would you care to join me, Doctor?”


End file.
